This invention relates to estimation of synthetic audio prototypes.
In the field of audio signal processing, the term “upmixing” generally refers to the process of undoing “downmixing”, which is the addition of many source signals into fewer audio channels. Downmixing can be a natural acoustic process, or a studio combination. As an example, upmixing can involve producing a number of spatially separated audio channels from a multichannel source.
The simplest upmixer takes in a stereo pair of audio signals and generates a single output representing the information common to both channels, which is usually referred to as the center channel. A slightly more complex upmixer might generate three channels, representing the center channel and the “not center” components of the left and right inputs. More complex upmixers attempt to separate one or more center channels, two “side-only” channels of panned content, and one or more “surround” channels of uncorrelated or out of phase content.
One method of upmixing is performed in the time domain by creating weighted (sometimes negative) combinations of stereo input channels. This method can render a single source in a desired location, but it may not allow multiple simultaneous sources to be isolated. For example, a time domain upmixer operating on stereo content that is dominated by common (center) content will mix panned and poorly correlated content into the center output channel even though this weaker content belongs in other channels.
A number of stereo upmixing algorithms are commercially available, including Dolby Pro Logic II (and variants), Lexicon's Logic 7 and DTS Neo:6, Bose's Videostage, Audio Stage, Centerpoint, and Centerpoint II.
There is a need to perform upmixing in a manner that accurately renders spatially separated audio channels from a multichannel source in a manner that reduces sonic artifacts and has low processing latency.